1. Field of the Invention
This invention relates to locks and has particular reference to electrically controlled security locks used on safes and the like.
2. Description of the Prior Art
Although many different types of electrically controlled security locks have been used heretofore, it has been found that the simplest and most practical types utilize a lock bolt which is spring pressed into its locking position and is retracted into unlocking position by an electromagnetically operable device such as a solenoid. However, such locks have certain drawbacks which may permit unauthorized opening thereof by persons familiar with their construction and manner of functioning. Where the lock is incorporated in a safe, such a person would, for example, be aware that the safe could be dropped while in a position such that upon landing the momentum of the bolt would compress the spring and cause the bolt to move into its unlocking position. The same result could be achieved if the safe were given a heavy blow in a direction opposite to the direction of movement of the bolt. This type of blow causes the bolt, because of its inertia, to retract into said unlocking position.
In a safe with a lock of the above-described type, where a hole in the safe's door exists or is made by drilling, the lock can be released by forcing a suitable tool through the hole to dislodge the lock mechanism, or a part thereof, from its mooring on the door and thus disable the bolt.